HTML5 Canvas Floating Particles responsive fix?

What I have is an overlaying canvas element with floating particles that bounce around the screen, meant to mimic floating leaves and/or dust particles. The canvas element overlays a scenic background, and when the page is viewed on a mobile device the particles seem too large to be viewed as floating leaves/dust, they look like balls floating around which hinders the imagination of them being leaves/dust.

I'm wanting to resize the particles when the browser screen is smaller than 600px, and I'm not sure how to modify the code to do so.